Blasphemous Act

Oracle Text

This spell costs 1 less to cast for each creature on the battlefield.

Blasphemous Act deals 13 damage to each creature.

Card Rulings

9/22/2011 The total cost to cast Blasphemous Act is locked in before you pay that cost. For example, if there are three creatures on the battlefield, including one you can sacrifice to add to your mana pool, the total cost of Blasphemous Act is . Then you can sacrifice the creature when you activate mana abilities just before paying the cost.
9/22/2011 Blasphemous Act’s ability can’t reduce the total cost to cast the spell below .
9/22/2011 Although players may respond to Blasphemous Act once it’s been cast, once it’s announced, they can’t respond before the cost is calculated and paid.